One of the reasons that astronomy appeals to so many people are the stunningly beautiful photographs of nebulae throughout our galaxy. Tomorrow’s edition of the journal Nature features a paper that explains just how a cloud of gas was twisted and formed into a double helix shape. NASA’s Spitzer Infrared Telescope took this color-enhanced image of the nebula.
Twisting and interacting magnetic fields near the center of the galaxy are probably the culprit here, according to the article (see the citation below). When viewed in this broader-context image (taken using the Midcourse Space Experiment satellite), the twisting double helix nebula appears to be emerging nearly vertically out of the galactic plane. This fact, combined with the temperature of the gases and their proper motions provide strong evidence that the galaxy’s central magnetic field has sculpted this nebula.
Of course, the scientific and rational reason for this nebula’s existence are perfectly clear. But, like much in astronomy the striking beauty of a life-like form replicated on the enormous stage of the heavens seems to speak to a deeper role of life in the universe. Unlike many celestial images, this double helix would be visible to all viewers in the entire galaxy. Perhaps they, if they exist, also posses twisted-pair nucleotide genetic material. Perhaps their infrared telescopes have taken this same picture, and they have been struck with the same sense of wonder and awe as we are.
But then again, this isn’t Star Trek, and alien life don’t by any means necessarily have DNA, if they even exist. Nevertheless, a beautiful image and an active imagination just brightened my day. I hope you enjoy it just as much!
Citation
Morris, M, Uchida, K, Do, T (2006). “A magnetic torsional wave near the Galactic Centre traced by a ‘double helix’ nebula.” Nature 440(7082), pp. 308-310 [online at CiteULike.org]
Why are galaxies / solar systems planar?
“…the striking beauty of a life-like form replicated on the enormous stage of the heavens seems to speak to a deeper role of life in the universe.”
Exploited to the max by Kim Stanley Robinson’s _Red Mars_, in which the falling/burning space elevator reveals its double-helical core of synthetic diamond, glowing white-hot in the sky. I’m not sure it made even hand-waving sense as materials science or engineering, but it sure delivered the symbolism.
Monte,
It’s been years since I read “Red Mars”. Thanks for reminding me of that symbolism!
Tom, here’s what I remember from my astronomy classes:
It’s largely to do with conservation of angular momentum, though not all galaxies are planar, and not all of the parts of a “typical” solar system are either. Spiral galaxies and solar systems are mostly planar because as a large gravitationally-bound cloud of gas (i.e. one in which the gas can be considered contained by its own mass) collapses under its own weight, even a slight initial rotation of the cloud will cause the cloud to flatten. The true answer is, of course, much more complicated.
There are parts of our galaxy that are non-planar (including the spherically-distributed globular clusters, and the much less-dense halo of relatively dark objects surrounding the galactic disk) that are thought to be “remnants” of an earlier stage of galactic evolution.
Our solar system has a vast constellation of spherically-distributed (we think) cometary cores called the Oort Cloud. These icy bodies are the source of most of the comets we see in the sky. One explanation for their distribution is that they are the result of countless interactions between large planets like Jupiter or Saturn and the many trillions of planetessimals that formed in the first few million years of the universe. When the planetessimals came near the gas giants, they were very nearly ejected from the solar system, but instead ended up in solar orbits at distances of as much as a light-year away.
Also, it is now believed that elliptical-type galaxies form when two spiral galaxies collide. These galaxies are described with the shape “oblate-spheroid”, meaning like a football, because of the relatively random distributions of angular momentum after the collision takes place.
“The true answer is, of course, much more complicated.”
Five words: “broken symmetry” and “unstable against perturbation.” There — wasn’t that easy?
An algebraic topologist could probably do it rigorously in a few lines. Of course, it wouldn’t be quantitative, and I gather you astro/ME types are compulsive about that.